1. Field
The embodiments herein relate to a method and apparatus for determining optimal projection images of an object of interest, particularly angiographic images.
2. State of the Art
X-ray angiography is a commonly used imaging modality within a numerous variety of interventions. During the interventions, it is very important that the clinician achieves a good understanding of the object in question using a workflow that is as efficient as possible. That is, a method that is fast, reproducible and burdens the patient minimally.
During X-ray angiography several different two-dimensional images, also called two-dimensional projections, of the object under examination can be obtained from different views or perspectives by rotating the arm, holding the X-ray source and the image intensifier, with reference to the patient.
It is common practice to use two acquired two-dimensional angiographic images to generate a three-dimensional reconstruction for example a part of the vascular system. This three-dimensional reconstruction is then the basis for performing 3D quantitative analysis on (part of) a vessel of interest or for instance to perform computational fluid dynamic simulations.
Because the three-dimensional reconstruction is the basis for further calculations, it is important that the three-dimensional reconstruction is as accurate as possible. The choice of the two two-dimensional angiographic images is determinative for the accuracy of the three-dimensional reconstruction.
This is due to different aspects. First of all, the two two-dimensional images used to generate the three-dimensional reconstruction should contain as much information regarding the object of interest as possible.
Furthermore, the accuracy of the three-dimensional reconstruction is not solely dependent on the amount of information that is present in the two two-dimensional angiographic images, as the spatial angle between the two images is of importance. When the spatial angle between the two two-dimensional angiographic images is too small, the geometry of the vessel is unclear because the images contain roughly the same information regarding the object of interest.
At the moment, several methods have been proposed to determine optimal views or perspectives at which the clinician should acquire two-dimensional angiographic images to allow accurate 3D reconstruction. These optimal views are however determined using 3D information of the object of interest as described for instance in U.S. Pat. No. 9,129,418. In practice this means that a clinician acquires two two-dimensional angiographic images. These images are then used to generate a three-dimensional reconstruction which is subsequently used to determine the optimal perspective(s). It is not until after generating the three-dimensional reconstruction that the clinician obtains information on how optimal the two two-dimensional angiographic images are that were used to generate the three-dimensional reconstruction. If the used two two-dimensional images were not optimal, the clinician has to acquire a new two two-dimensional angiographic image and generate a new three-dimensional reconstruction or at least one according to the teachings of European patent application published with number EP2570079.
A large disadvantage of these approaches is that a 3D reconstruction of the object of interest is required to determine if the used two-dimensional projections are optimal. Because of this, a complete analysis of the images has to be performed before the initially chosen image projections can potentially be replaced with more optimal projections. This is time consuming and poses a burden on the patient in terms of more contrast fluid as well as more exposure to x-ray radiation.
There is therefore a need for a more efficient approach that optimizes the workflow for the clinician and reduces the burden to the patient.